1. Field of the Invention
The invention relates to a transmitter device, in particular for a base transceiver station in a mobile radio network, a modulation closed loop which can be used in such a transmitter device, and a digital phase/frequency discriminator which is suitable for use in such a modulation closed loop.
2. Related Art
One of the most exacting requirements which is made of a GSM transmitter is its compliance with the GSM specifications in terms of the out-band noise and the interference of the GSM transmitter in the receiver band. The reason for this is the fact that the transmitter and receiver can be operating simultaneously and the separation between the transmitter band and the receiver band is 10 MHz at minimum. Hitherto, in order to comply with the specifications, filters were used at the output of the base stations. These filters are expensive owing to the required high level of signal coherence and steep edges, and the transmission power which can be effectively used is unnecessary owing to its insertion loss which has to be compensated again by a higher power output stage.
For this reason, the invention is based on making available a transmitter device, a modulation closed loop and a digital phase/frequency discriminator which fulfil the above mentioned GSM specifications and the requirements made of the output filter of a transmitter and reduce the costs of that transmitter.